1. Field of the Invention
The present invention relates to a strand feeding device, more particularly to a strand feeding device for a coaxial cable braiding apparatus.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional strand feeding device 1 for a coaxial cable braiding apparatus is shown to include: a seat body 11 extending in a longitudinal direction and having a top end 110xe2x80x3 defining a top end face 110, a mounting bore 112 extending inwardly and downwardly from the top end face 110 in the longitudinal direction, and a side face formed with a slot 113 that extends in the longitudinal direction and that is in spatial communication with the mounting bore 112; a bobbin-mounting post ill extending uprightly from the top end face 110 in the longitudinal direction; a bobbin 13 sleeved rotatably around the bobbin-mounting post 111 and having a lower end formed with a plurality of angularly spaced apart engaging grooves 114, each of which is confined by a groove-defining wall 115 that has a flat wall portion 115F; and a limiting member 15 including a spring biased rod 152 disposed movably in the mounting bore 112, and a protrusion 153 extending outwardly and transversely from the rod 152 through the slot 113. The rod 152 has a top portion formed with a flat abutment surface 152F that is vertically aligned with a selected one of the engaging grooves 114 in the lower end of the bobbin 13. The rod 152 is movable in the longitudinal direction between an upper position, in which the top portion of the rod 152 extends into the selected engaging groove 114 and the flat abutment surface 152F of the rod 152 abuts against the flat wall portion 115F of the groove-defining wall 115 of the selected engaging groove 114 so as to prevent rotation of the bobbin 13 relative to the bobbin-mounting post 111, and a lower position, in which the top portion of the rod 152 retracts into the mounting bore 112 and disengages from the selected engaging groove 114 so as to permit rotation of the bobbin 13 relative to the bobbin-mounting post 111. An urging member 151 is disposed in the mounting bore 112 for urging the rod 152 to move to the upper position. A swinging arm 14 is pivoted to the seat body 11 through a pivot shaft, and is disposed adjacent to the protrusion 153 of the rod 152. The swinging arm 14 is turnable about the pivot shaft between a released position, in which the swinging arm 14 presses the protrusion 153 against urging action of the urging member 151 to move the rod 152 to the lower position, and a locking position, in which the swinging arm 14 moves away from the protrusion 153 so as to permit restoring of the rod 152 to the upper position by the urging action of the urging member 151.
One disadvantage of the aforesaid conventional strand feeding device 1 resides in that when the rod 152 is moved to the upper position, the flat abutment surface 152F of the rod 152 fully abuts against the flat wall portion 115F of the groove-defining wall 115 of the aligned engaging groove 114 to prevent rotation of the bobbin 13 relative to the bobbin-mounting post 111. As a result, a relatively large amount of friction is present between the rod 152 and the bobbin 13 that tends to expedite wearing of the groove-defining wall 115 and that consequently shortens the service life of the conventional strand feeding device 1.
Therefore, the object of this invention is to provide a strand feeding device for a coaxial cable braiding apparatus, which includes a rod with a rounded surface, that is capable of overcoming the aforesaid drawback of the prior art.
A strand feeding device for a coaxial cable braiding apparatus according to the present invention includes: a seat body extending in a longitudinal direction, and having a top end defining a top end face, a mounting bore extending inwardly and downwardly from the top end face in the longitudinal direction, and a side face formed with a slot that extends in the longitudinal direction and that is in spatial communication with the mounting bore; a bobbin-mounting post extending uprightly from the top end face of the seat body in the longitudinal direction; a bobbin sleeved rotatably around the bobbin-mounting post and having a lower end formed with a plurality of angularly spaced apart engaging grooves, each of which is confined by a groove-defining wall; a limiting member including a spring-biased rod disposed movably in the mounting bore and a protrusion extending outwardly and transversely from the rod through the slot, the rod having a top portion that has a rounded surface and that is vertically aligned with a selected one of the engaging grooves in the lower end of the bobbin, the rod being movable in the longitudinal direction between an upper position, in which the top portion of the rod extends into the selected one of the engaging grooves and the rounded surface of rod abuts against the groove-defining wall of the selected one of the engaging grooves so as to prevent rotation of the bobbin relative to the bobbin-mounting post, and a lower position, in which the top portion of the rod retracts into the mounting bore and disengages from a vertically aligned one of the engaging grooves so as to permit rotation of the bobbin relative to the bobbin-mounting post; an urging member disposed in the mounting bore for urging the rod to move to the upper position; and a swinging arm pivoted to the seat body through a pivot shaft that extends in a transverse direction relative to the slot. The swinging arm is disposed adjacent to the protrusion of the rod, and is turnable about the pivot shaft between a released position, in which the swinging arm presses the protrusion against urging action of the urging member to move the rod to the lower position, and a locking position, in which the swinging arm moves away from the protrusion so as to permit restoring of the rod to the upper position by the urging action of the urging member.